Angiogenesis is the fundamental process by which new blood vessels are formed and is essential to a variety of normal body activities (such as reproduction, development and wound repair). Although the process is not completely understood, it is believed to involve a complex interplay of molecules which both stimulate and inhibit the growth of endothelial cells, the primary cells of the capillary blood vessels. Under normal conditions these molecules appear to maintain the microvasculature in a quiescent state (i.e., one of no capillary growth) for prolonged periods that may last for weeks, or in some cases, decades. However, when necessary, such as during wound repair, these same cells can undergo rapid proliferation and turnover within as little as five days.
Although angiogenesis is a highly regulated process under normal conditions, many diseases (characterized as “angiogenic diseases”) are driven by persistent unregulated angiogenesis. Otherwise stated, unregulated angiogenesis may either cause a particular disease directly or exacerbate an existing pathological condition. For example, the growth and metastasis of solid tumors have been shown to be angiogenesis-dependent. Based on these findings, there is a continuing need for compounds which demonstrate antiangiogenic activity due to their potential use in the treatment of various diseases such as cancer. Peptides having angiogenesis inhibiting properties have been described in commonly-owned WO01/38397, WO01/38347, WO99/61476, and U.S. patent application Ser. No. 09/915,956. However, it would be desirable to prepare antiangiogenic compounds having improved profiles of activity and smaller size.